Conventionally, for example, as described in Patent Literature No. 1, Patent Literature No. 1 proposes a current sensor including: a core for providing a first magnetic flux according to the measurement object current, the core formed to have a ring shape with a gap and to surround a part of a current path, in which current (i.e., the measurement object current) as a measurement object flows; and a magnetic sensor arranged in the gap. The above described core is formed by multiple layers, which are stacked and made of magnetic material having a plate shape.
Here, it is considered that, in the current sensor described in Patent Literature No. 1, the number of stacking layers made of magnetic material increases so as to restrict magnetic saturation of the core, and a cross sectional shape of the core perpendicular to a flowing direction of the first magnetic flux is enlarged. When the cross sectional shape is enlarged, a demagnetizing field for reducing a density of the first magnetic flux increases. Thus, the magnetic saturation of the core is restricted. However, when the measurement object current is an alternating current, the following difficulties may arise.
When the alternating current flows in the current path, an eddy current for generating a magnetic field, which cancels the first magnetic flux, arises in the core. In view of a macroscopic perspective, one large eddy current seems to be generated at an outer skin of the core. The larger the cross sectional area of the core and the shorter a total length of the outline of the outer shape of the cross sectional shape of the core, the larger the macroscopic eddy current. Accordingly, even if the cross sectional area of the core is enlarged in order to restrict the magnetic saturation of the core, a distribution of the first magnetic flux flowing through the core may be varied by the eddy current, so that a detection accuracy of the current is reduced.